1. The Field of the Invention
The present invention relates generally to the production of commercial fertilizers by treating agricultural and industrial wastes. More specifically, the present invention relates to a method for producing organic-based, slow release fertilizers by processing organic-based and industrial wastes.
2. The Relevant Technology
Feedlots, animal barns, agroindustrial plants, municipal sewage, and farms that keep large numbers of animals are sources of enormous quantities of organic waste. The expression xe2x80x9corganic waste sourcexe2x80x9d will hereinafter refer to any of these sources of organic waste or to any source that similarly produces organic waste, although perhaps in different quantities or by different activities.
The disposal of untreated organic waste causes serious pollution problems which include those due to the waste""s high content of chemically oxidizable components (expressed as COD, or chemical oxygen demand) and biochemically decomposable components (expressed as BOD, or biochemical oxygen demand). When these pollutants reach bodies of water, either because they leach from disposal sites or as a consequence of being directly released or transported into water bodies, they deoxygenate the receiving waters and impair the receiving waters"" capability to support aquatic life.
Acridity and high pathogen content add to the COD and BOD problems of untreated waste disposal. Acrid gases released into the atmosphere are not only unpleasant but they can also contribute to acid deposition, global greenhouse effects, and ozone depletion.
According to background material provided by the US Environmental Protection Agency (EPA), xe2x80x9canimal waste, if not managed properly, can run off farms and pollute nearby water bodies. Agricultural run off, rich in nutrients like nitrogen and phosphorous has been linked to dangerous toxic microorganisms such as Pfisteria piscicida. Pfisteria is widely believed to be responsible for major fish kills and disease events in several mid-Atlantic states and may pose a risk to human health.xe2x80x9d Draft Strategy for Animal Feeding Operations, EPA Memorandum, Mar. 4, 1998. See also EPA To Better Protect Public Health and The Environment From Animal Feeding Operations, EPA release of Mar. 5, 1998. In particular, the relationship between swine production and waste management problems has been reported in the Task Force Report No. 124, Council for Agricultural Science and Technology, Waste Management and Utilization in Food Production and Processing, October 1995, pp. 42-54, 110-121.
Notwithstanding the problems referred to above and other detrimental effects of the disposal of untreated organic waste, organic waste has nutritional value for plants. Nevertheless, untreated organic waste cannot be used directly as fertilizer because of the afore-mentioned problems. The alternative use of synthetic fertilizers is often adopted for increasing crop yield, but this solution carries at least two undesirable implications. First, a strategy that relies only on the use of synthetic fertilizers neglects the problem of organic waste disposal. Second, the manufacture of synthetic fertilizers frequently requires consumption of considerable amounts of energy and possibly expensive synthesis materials, sometimes involves polluting subprocesses, and may produce additional waste whose safe disposal is often expensive. In addition, the fast release of most synthetic fertilizers causes leaching, which in turn leads to wasted fertilizer and the ensuing pollution problems when the leached fertilizer accumulates in canals and other bodies of water.
The problems inherent to organic waste production and subsequent treatment require economical processes which avoid the afore-mentioned environmental problems. The efficiency of these processes is considerably enhanced when, in addition to providing a practical disposal of organic waste, the processes convert the organic waste into a useful product, such as commercial fertilizer, preferably a slow-release fertilizer. This conversion requires the recovery of the nitrogenous products in the waste and their conversion into a fertilizer that can slowly release nitrogen in a form that plants can absorb. Because of the diversity of variables that determine the economic, chemical, and environmental aspects of this conversion problem, a variety of attempts to treat organic waste have been undertaken. The patents and other works referred to hereinbelow relate to methods that address aspects of the problem of converting organic waste into useful fertilizer.
Methods for producing fertilizer have been disclosed in references that include the following patents and articles.
U.S. Pat. No. 5,593,099 describes a method for producing fertilizer from liquid manure or from sludge that includes mixing the manure or sludge with harvest leftovers and then grinding the mixture to a particle size such that the particles adsorb and absorb the liquid substance fully. An apparatus for producing the solid fertilizer is also disclosed.
U.S. Pat. No. 5,482,528 describes a pathogenic waste treatment process to produce a useful product such as an amendment to agricultural land. In the process, waste is combined with an acid and a base which react exothermically to thermally pasteurize the waste and add mineral value to the product. Materials such as fly ash agglomerate the product, and after grinding, the particles can aerate the soil. This patent is a division of U.S. Pat. No. 5,422,015 that also discloses a pathogenic waste treatment. The use of alkaline fly ash as an amendment for swine manure has been studied by M. Vincini, F. Carini, and S. Silva, Use of Alkaline Fly Ash as an Amendment for Swine Manure, Bioresource Technology, Vol. 49 (1994), pp. 213-22.
U.S. Pat. No. 5,443,613 describes a method for producing suspension fertilizer by first preparing an aqueous initial suspension of the organic material and transforming it into colloidal form. An ammoniacal compound, such as anhydrous or aqueous ammonia, and supplemental compound or compounds for providing the other desired inorganic plant nutrients are added to and admixed with the acidified suspension to produce a finished suspension fertilizer having the desired analysis.
U.S. Pat. No. 5,411,568 describes a method for preparing granular slow release nitrogen fertilizer from nitrogenous organic wastes by coreacting particulate dry conditioned nitrogenous organic waste and reactive ureaformaldehyde oligomer.
U.S. Pat. No. 5,393,317 describes a method and apparatus for making organic based fertilizer, the method including mixing organic material with phosphate, potash, or other inorganics and water if necessary. Acid and ammonia are also added to the mixture, and quantities of the various ingredients are adjusted to provide a fertilizer that has a desired percentage of the major fertilizer elements for a specific crop.
U.S. Pat. No. 5,378,257 describes a process for organic fertilizer production that comprises mixing a batch of the waste matter with nitric acid, crushing the waste water mixed with nitric acid to make sludge, adding quicklime to the sludged waste matter, thereby neutralizing the waste water, and during the neutralized waste matter. An apparatus for the production thereof is also disclosed.
U.S. Pat. No. 5,071,559 discloses a method for processing manure by adding an organic carrier liquid to the manure, concentrating the mixture of manure and carrier liquid, condensing the formed vapor, anaerobically treating the condensate, and aerobically treating the effluent from the anaerobic treatment.
U.S. Pat. Nos. 5,021,247, 5,021,077, and 4,997,469 disclose methods for preparing high integrity natural nitrogenous granules for agriculture by processes that include the heating of natural nitrogenous materials under alkaline conditions until the materials develop adhesive properties.
U.S. Pat. No. 4,710,300 describes a method for processing of organic materials containing nitrogen compounds, where the organic material undergoes an anaerobic digestion with simultaneous liberation of biogas which contains methane and carbon dioxide. In this process, the liquid product obtained after anaerobic digestion is heated to boiling temperature, ammonia is bonded as carbonate which is distilled off, and the tail product from distillation is further processed to the valuable product and clear water or is discharged as prepurified wastewater. Biogas production and anaerobic lagoon digesters have been described by L. M. Safley, Jr., S. L. Crawford, and W. R. McLeod, Capturing Methane for Fuel and Other Strategies for Managing Swine Lagoon Waste, pp. 38-41; L. M. Safley, Jr., S. L. Crawford, D. Nichols, and W. R. McLeod, Low Temperature Lagoon Digester for Biogas Production from Swine Manure; L. M. Safley, Jr., and P. D. Lusk, Low Temperature Anaerobic Digester, published by the Energy Division of the North Carolina Department of Economic and Community Development; J. R. Fischer, D. M. Sievers, and C. D. Fulhage, xe2x80x9cAnaerobic Digestion in Swine Wastesxe2x80x9d, and E. J. Krocker, H. M. Lapp, D. D. Schulte, and A. B. Sparling, xe2x80x9cCold Weather Energy Recovery from Anaerobic Digestion of Swine Manurexe2x80x9d, in: Energy, Agriculture and Waste Management, edited by W. A. Jewell, (Ann Arbor Science, 1975) pp. 307-16, 337-52 .
European Patent Application No. 79400246.9 discloses a method and facility for deodorizing waste from pig farms and for transforming it into manure. A mixture of the waste and a calcareous solution is decanted and the separated liquid component is oxygenated by compressed air. Odor control methods have been described by S. Barrington and K. El Moueddeb, xe2x80x9cZeolite to Control Swine Manure Odours and Nitrogen Volatilizationxe2x80x9d, in: New Knowledge in Livestock Odor Solutions, International Livestock Odor Conference ""95, pp. 65-68, and S. Piccinini, Application of a Phillipsite Rich Zeolite During the Composting of Solid Fractions of Pig Slurry, Materials Engineering, Vol. 5 no. 2 (1994), pp. 375-81.
Methods for treating wastewater have been disclosed in references that include the following patents and articles.
U.S. Pat. No. 5,545,326 describes a pressurized process for the treatment of high-solids wastewater having relatively high BOD and phosphorous concentration that includes anaerobic and aerobic treatment. The treated wastewater effluent is discharged in an environmentally safe manner such that the residue BOD and phosphorous are concentrated in the solid fraction which may be a source of protein. U.S. Pat. No. 5,266,201 describes a process for the purification of aqueous solutions polluted by nitrate ions, such as municipal wastewater, factory effluents, and liquid manure.
U.S. Pat. No. 4,872,993 discloses processes and techniques for treating wastewater to remove organic matter and heavy metals. In the treatment, clay and flocculating agent are added to the wastewater to cause separation of a sludge. Research on unsettleable material removal by chemical coagulation and flocculation has been reported by M. Hanna, D. M. Sievers, and J. R. Fischer, xe2x80x9cChemical Coagulation of Methane Producing Solids from Flushing Wastewatersxe2x80x9d, in: Agricultural Waste Utilization and Management, Proceedings of the Fifth Int. Symposium on Agricultural Wastes, Dec. 16-17, 1985, pp. 632-37, and by D. M. Sievers, Rapid Mixing, Influences on Chemical Coagulation of Manures, Biological Wastes, Vol. 28 (1989), pp. 103-14.
U.S. Pat. No. 4,519,831 describes a method of converting sewage sludge solids into dense controlled release, attrition resistant fertilizer agglomerates. The method uses acidic material and uncondensed liquid ureaform. U.S. Pat. No. 4,245,396 discloses a process for drying and granulating sewage sludge either mechanically or by application of heat. This patent is related to U.S. Pat. No. 4,193,206 on processes for drying sewage sludge and filtering water, and to U.S. Pat. No. 4,128,946 on a drying organic waste process.
European Patent Application No. 83830277.6 discloses a method for removing and recovering ammonium, potassium and phosphate ions from wastewater by selective nutrient removal using ion-exchange resins, resin regeneration and recovery of nutrients and precipitation of hydrous MgNH4PO4 and/or MgKPO4. This is a RIM-NUT process, where RIM-NUT stands for xe2x80x9cremoval of nutrients.xe2x80x9d This process has also been disclosed in other publications, such as L. Liberti, A. Lopez, V. Amicarelli, and G. Boghetich, xe2x80x9cAmmonium and Phosphorous Removal from Wastewater Using Clinoptilolite: A Review of the RIM-NUT Processxe2x80x9d, in: Natural Zeolites ""93, pp. 351-62; S. J. Kang, T. W. King, P. J. Horvatin, A. Lopez, L. Liberti, and L. Beebe, Nutrient Removal and Recovery from Municipal Wastewater by Selective Ion Exchange, and L. Liberti and A. Lopez, xe2x80x9cApplications of a New Physicochemical Method for Removal and Recovery of Nutrients from Wastewaterxe2x80x9d, in: Nutrient Removal from Wastewater, edited by N. J. Horan, P. Lowe, and E.I. Stentiford (1994), pp. 371-78. The formation of magnesium ammonium phosphate hexahydrate (struvite) has been studied by C. Maqueda, J. L. Perez Rodriguez, and J. Lebrato, Study of Struvite Precipitation in Anaerobic Digesters, Water Research Vol. 28 (1994), pp. 411-16, and by K. M. Webb and G. E. Ho, Struvite (MgNH4PO4.6H2O) Solubility and its Application to a Piggery Effluent Problem, Water Science and Technology Vol. 26 (1992), pp. 2229-32. The precipitation of phosphate and ammonia and nutrient removal from swine wastewater has been studied by E. Brione, G. Martin, and J. Morvan, xe2x80x9cNon-Destructive Technique for Elimination of Nutrients from Pig Manurexe2x80x9d, in: Nutrient Removal from Wastewater, edited by N. J. Horan, P. Lowe and E.I. Stentiford, (Technomic Pub., 1994) pp. 33-37; P. H. Liao, Y. Gao, and K. V. Lo, Chemical Precipitation of Phosphate and Ammonia from Swine Wastewater, Biomass and Bioenergy, Vol. 4 no. 5 (1993), pp. 365-71, and by Y. C. Gao, P. H. Liao, and K. V. Lo, Chemical Treatment of Swine Wastewater, Journal of Environmental Science and Health, Vol. A28 no. 4 (1993), pp. 795-807.
Fertilizer compositions and/or fertilizer components have been disclosed in references that include the following patents.
U.S. Pat. No. 5,549,730 relates to a compression molded tablet fertilizer capable of slowly releasing active ingredients and is suitable for use in horticulture and afforestation, and a method for the production thereof.
U.S. Pat. No. 4,845,888 describes a multilayer degradable and controlled release multinutrient mulch film, and a process of preparing it. U.S. Pat. No. 4,832,728 reveals fertilizer compositions, processes of making them, and processes of using them. This patent is a division of U.S. Pat. No. 4,560,400 that relates to a fertilizer in granular form, and processes for making and using it. U.S. Pat. No. 4,743,287 discloses a fertilizer and a method for making a complex humic acid fertilizer by mixing a select organic material, water, and measured amounts of major inorganic elements of nitrogen, phosphate, potash and sulfur.
U.S. Pat. No. 5,433,766 reveals a synthetic apatite containing agronutrients and a method for making the apatite. The apatite comprises crystalline calcium phosphate having agronutrients dispersed in the crystalline structure, and it can optionally comprise a carbonate and/or silicon solubility control agent. The agronutrients are released slowly as the apatite dissolves. U.S. Pat. No. 5,055,124 reveals the production of potassium phosphate useful as a low-chloride content fertilizer by reacting phosphoric acid, commercial or technical grade, with fertilizer-grade potassium chloride. The reaction product is used to produce various types as well as grades of fertilizers.
Methods that include fermentation or the use of certain microorganisms have been disclosed in references that include the following patents.
U.S. Pat. No. 5,118,336 discloses a method for valorizing liquid manure from pigs by elaboration of biological amendments. The method includes fermentation of a biomass based on a mixture of pig liquid manure and a carbonaceous medium. U.S. Pat. No. 4,795,711 describes the fermentation of organic materials for producing heat and fertilizer. U.S. Pat. No. 5,093,262 discloses a method and apparatus for producing organic fertilizer with the use of nitrogen fixing bacilli.
Other treatments, production methods or compositions that relate to organic wastes have been disclosed in references that include the following patents.
U.S. Pat. No. 5,087,474 particularly relates to a method of recovering particulate animal feed fats, free of malodors and pathogens from abatoir by-products and to the product recovered by this method.
U.S. Pat. No. 4,765,900 describes a method for treating organic waste, which includes separating the liquid portion of the waste from the solid portion prior to reacting the solid portion in an accelerated wet oxidation reaction. U.S. Pat. No. 4,278,699 describes a method of purifying distillers solubles and use of the purified matter.
U.S. Pat. No. 4,310,552 discloses a swine, hog and pig fodder which comprises the customary digestible meal or grain component in combination with an indigestible blown perlite additive.
U.S. Pat. No. 4,109,019 is directed to a method for producing feeds for ruminant animals whereby carbamides, particularly urea and biuret, are reacted with fermented proteinaceous agricultural products and wastes with the aid of an aliphatic dicarboxylic acid catalyst to produce feed which releases protein and protein equivalent nitrogen in a slow and controlled manner in the rumen.
U.S. Pat. No. 4,176,090 describes interlayered clay compositions used as catalysts, catalytic supports, and sorbents.
Despite the plurality of methods for treating organic waste and for producing fertilizer, conventional methods leave unsolved problems. This is particularly the case regarding strategies that rely on encompassing and integrating organic waste treatment methods and fertilizer production processes for making fertilizer with desired environmental and agronomical properties. More specifically, there is a need for commercially successful organic waste treatment and fertilizer production processes.
The composition of animal waste depends on both the kind of animal and the way the waste is handled. Poultry operations generally produce dry waste, with about 15%-25% moisture whereas hogs and cattle generate waste that is more liquid. In addition, water is typically used to flush hog and cattle waste out of barns and into storage facilities, thus producing a slurry that can be up to 97% liquid and it is typically stored either in earthen lagoons or in slurry tanks. In these conventional treatments, xe2x80x9cmany of the solids (including much of the phosphorous) settle into a sludge at the bottom. Most nitrogen remains dissolved in the water or volatilizes into the atmosphere. A farmer who utilizes the animal waste for nutrients pumps the liquid out for nutrients or irrigation, and may agitate the sludge at pumping time to capture the nutrients that otherwise would remain behind.xe2x80x9d Animal Waste Pollution in America: An Emerging National Problem, Environmental Risks of Livestock and Poultry Production, Report Compiled by the Minority Staff of the US Senate Committee on Agriculture, Nutrition, and Forestry for Sen. Tom Harkin, December 1997.
Most methods that rely on conventional lagoons do not clarify the effluent that carries the organic waste prior to its accumulation in the lagoon system. This practice leads to unnecessarily high loading of the lagoon system, thus requiring large conventional lagoons. Whereas some recently introduced lagoon treatments claim to reduce odors, these treatments essentially increase greenhouse gas emissions, such as carbon dioxide and ammonia gas emissions.
In anaerobic lagoons, one of the more common methods of hog manure treatment, organic matter in the waste is decomposed by bacteria. These lagoons are under increased criticism for the offensive odor that results from incomplete decomposition and ground water contamination. Anaerobic lagoons also diminish nutrient value in the hog wastes through processes that include the loss during digestion of much of the nitrogen in the waste.
The removal of eutrophic ions from wastewater and the reintroduction of nitrogen and phosphorus into the environment is the focus of some methods that nevertheless do not address the recovery of biogas that has considerable energetic value and whose release into the atmosphere can have a serious impact on air quality, ozone concentration, and global climate changes. In addition, recovered biogas can be used for heating or electric energy generation. Whereas the capture of the gases released in the conversion of organic waste to fertilizer leads to a reduction or elimination of undesirable odors, greenhouse gas emissions, and gases that can contribute to acid deposition, some methods that focus on the elimination of odors or pathogenic content of organic waste do not provide for the conversion of waste into a commercial fertilizer.
After biogas recovery, the sludge that can be separated from the organic waste effluent contains ammonia and phosphates that are recoverable by precipitation under controlled pH conditions. The densified precipitate is a fertilizer that can be supplemented with other compounds to incorporate in its composition micronutrients and to standardize its composition, but most organic waste treatments neglect the incorporation of these complements that are necessary for plant growth, and more specifically, for crop production.
Furthermore, the conversion of waste into fertilizer in most conventional organic waste treatments does not absorb residues produced by other activities. These residues include the waste generated by, for example, industrial mining and the combustion of coal in power plants.
It is also important that the reintroduction of phosphates and ammonia into the environment be achieved by means of a slow release fertilizer. Certain components in organic waste used as a source of plant nutrients far exceed plant demand when they are not properly administered. For example, It is acknowledged that phosphorous nonpoint-source pollution is becoming a problem throughout the USA. F. Liu, et at., Phosphorous Recovery in Surface Runoff from Swine Lagoon Effluent by Overland Flow, J. Environmental Quality Vol. 26 (1997) 995-1001. In addition, ammnonia is usually released from untreated pig slurry that is directly applied as a fertilizer. Ammonia loss rates have been reported as being very high during the first 4 hours to 6 hours after slurry application. These ammonia losses can be significantly enhanced by temperature and wind speed increases. Sven G. Sommner, et al., Ammonia Volatilization from Pig Slurry Applied with Trail Hoses or Broadspread to Winter Wheat: Effects of Crop Developmental Stage, Microclimate, and Leaf Ammonia Absorption, J. Environmental Quality Vol. 26 (1997) 1153-1160. In contrast with some processed organic waste, the slow release fertilizer produced according to this invention considerably decreases water pollution that would otherwise take place by leaching.
Finally, some methods produce variable composition fertilizers depending on the characteristics of the feed provided to the animals that produce the waste, thus supplying non-standard composition fertilizers. It would be desirable to produce a fertilizer of standard composition that can be appropriately modified to satisfy the needs of different agribusiness.
Currently, organic waste is largely treated and disposed of by relying on technology developed in the 1940""s for small scale operations, and integrated waste systems are nonexistent. In particular, most of the presently available waste treatment and disposal methodology relies on single unit operations which address a single problem or a very reduced number of problems. This approach cannot solve the variety of environmental, economical, operational, and technological problems that the multifaceted waste treatment and fertilizer production industry faces.
Descriptions of methods that address specific elements of the more encompassing problem of converting waste into useful fertilizer by an economical and nonpolluting process can be found in some of the afore-mentioned related art. Some of these methods necessitate the addition of materials such as caustic products, urea or formaldehyde. Others rely on sources of energy for heating or for oxygenating by forced air flow.
For example, the treatment of organic waste with caustic chemicals may eliminate the waste""s pathogenic content and render it suitable for its use in agriculture, but this method would not solve other problems such as the prevention of emissions of acrid odors and other gases that contribute to the greenhouse effect and to the depletion of ozone. In particular, some conventional methods aim at eliminating nitrogen compounds from the organic waste, but in doing so they also increase greenhouse gas and acrid gas emissions. In addition, these methods decrease the yield of nitrogen compounds in the final product into which the organic waste is processed. Such methods would not absorb other residues and waste that would have to be independently disposed of. They would not produce useful fuel material, and would require large processing facilities.
Another limitation faced by most conventional waste treatment methods is the inability to effectively treat large amounts of organic waste. This limitation becomes particularly relevant in a production framework in which large animal operations gain efficiency by raising a very large number of animals in controlled indoor environments which in turn produce enormous amounts of organic waste. See, for example, Warren Cohen, United States Deep In Manure, US News and World Report, Jan. 12, 1998, p. 46.
Modern farming operations must address the problems that are inherent to the confining of large numbers of animals in concentrated feeding operations. To this respect, it has been reported that more manure is produced in some areas of the US than can be safely applied to available crop land. See, for example, National Legislation Needed to Address Animal Waste Pollution, Senate Panel Told, BNA Environment Reporter, Vol. 28(49) (1998) pp. 2647-49, and Waste From Hog, Chicken Farms Growing at xe2x80x98Alarmingxe2x80x99 Rate, Group Says, BNA Environment Reporter, Vol. 28(48) (1998) pp. 2648-50.
Sewage waste water treatment faces some of the same problems and raises similar concerns. Whereas the US has been regarded as a leader in sewage management, and sewage-treatment technology has been described as a success story in 20th-century US, it has been asserted that significant commercial advantages have been significantly lacking in the past few decades. Moreover, existing treatment methods have been characterized as facing a number of inherent problems that must be overcome to make further progress in the next century. William J. Jewell, Resource-Recovery Wastewater Treatment, American Scientist Vol. 82 (1994) pp. 366-75.
Attempts in the industry to overcome the multifarious limitations that are inherent to single unit operations have failed to date because of the inability to implement them economically or because of operational and technical difficulties. This limited scope of the current waste treatment and disposal technology has lead to industry problems that have received intense scrutiny by the media. Therefore, an encompassing, integrated waste treatment system is a long felt, yet unsatisfied, need in this industrial sector. The need for an encompassing and integrated waste treatment system has been expressed in a plurality of articles, statements on public health impacts and studies and regulations on animal feeding operations.
The EPA and legislators have been increasingly sensitive to the problems caused by current organic waste disposal practices and they have been focusing on the need to address such problems. In particular, the development of scientifically valid limits on land application of manure has been called, and the EPA has been reported as planning to revise the feedlot effluent limitations guidelines for poultry and swine by 2001, and for beef and dairy cattle by 2002. See Federal Role in Animal Waste Control Should Be Limited, House Panel Told, BNA Environment Reporter, Vol. 29(3) (1998) pp. 178-79; Draft Strategy for Animal Feeding Operations, EPA Memorandum, Mar. 4, 1998, and Compliance Assurance Implementation Plan For Concentrated Animal Feeding Operations, Office of Enforcement and Compliance Assurance, EPA, Mar. 5, 1998.
Acridity problems have also been increasingly addressed by legislators and government agencies. For example, following a recommendation from the Missouri Department of Natural Resources, the State of Missouri Air Conservation Commission reportedly agreed on Feb. 3, 1998, to form a task force to analyze odor pollution issues related to large hog and poultry farms in the state. See Task Force to Study Odor Issues Relating to Large Hog, Poultry Farms, in BNA Environment Reporter, Vol. 28(40) (1998) p. 2134.
In addition to the focus on the problems that untreated organic waste discharge may cause, government strategies have also highlighted the need for developing new technological approaches for treating organic waste, pointing out in particular that the use of successful and innovative technological approaches should be encouraged and pursued. Draft of the Strategy for Addressing Environmental and Public Health Impacts From Animal Feeding Operations, EPA, March 1998, pp. 11-12.
Each of the afore-mentioned patents and elements of related art is hereby incorporated by reference in its entirety for the material disclosed therein.
It is desirable to dispose of organic waste that would otherwise pose a serious environmental problem. Instead of its mere disposal, it is desirable to treat the organic waste and convert it into useful products. This conversion process however, should not lead to other forms of pollution. Instead, the conversion process should optimally rely on methods that are not very energy demanding and that do not require the consumption of other substances of complex, expensive, or polluting manufacture. Conversion of organic waste to fertilizer and optionally to feed supplement, and biogas recovery are two desirable and beneficial activities that can make the waste treatment process economical. In addition, these activities can make of the waste treatment process a practical and effective alternative to environmentally impermissible disposal.
To achieve the desirable goal of eliminating water pollution, organic waste treatment must provide effluents in every separation and reaction step that meet EPA discharge standards. The accomplishment of this goal should be further complemented by the capture and effective use of gases that, if released from the organic waste, would contribute to acid deposition, ozone depletion, greenhouse effect, and whose acridity could be intolerable.
It is also desirable that the organic waste treatment products do not contribute to water pollution by leaching and that they become economical slow release commercial fertilizer. Finally, it is also desirable that the organic waste treatment process be carried out by implementing techniques and methods that lead to a minimization of the overall land surface dedicated to the entire organic waste conversion process.
The expression xe2x80x9corganic wastexe2x80x9d is used herein as a descriptive term that encompasses waste of organic origin whether in the form of effluent, solid, sludge, slurry, or any other form that can be produced in organic waste sources. Furthermore, it is an operation well known to those skilled in the art to convert waste in, say, solid form to effluent by flushing the solid waste with water, if such conversion were needed at any step in the organic waste treatment and conversion process that is described and claimed below.
The objectives of this invention include the following. The general objective is to provide a method for the treatment of organic waste, whereby the organic waste is converted into commercial fertilizer, biogas useful for heating and power generation, and final effluents that can be directly employed in irrigation and wetland projects. In particular, the organic waste to be treated according to the methods of this invention can be, for example, hog farm effluent and solid matter, cattle or poultry waste.
It is a further objective of this invention to provide a method for the treatment of organic waste and production of supplement feed for animals, including cattle feed quality products.
Whether this invention is characterized as providing a method for producing fertilizer or for producing fertilizer and feed supplement, these characterizations are merely concise references to another objective of this invention that consists of providing a method for producing fertilizer only, feed supplement only, or both fertilizer and feed supplement.
It is a further objective of this invention to significantly reduce or even eliminate the release of gases that can lead to acrid odors, loss of potential plant nutrients, and environmentally undesirable emissions of gases that may contribute to acid deposition, ozone depletion and an overall insalubrity of local farming environments. This reduction or even elimination of release gases can be achieved in this invention by employing gas adsorbing substances, in particular ammonia adsorbing zeolites, at several stages of the waste generation and/or waste treatment processes, by reacting ammonia with acids, such as phosphoric or sulfuric acid, and by recovering methane-rich biogas.
The utilization of gas-adsorbing substances such as zeolites according to this invention minimizes the emission of ammonia gas from the animals"" gastrointestinal tracks and from the organic waste itself. The biogas can be directly used in the integrated waste treatment and fertilizer and feed supplement production processes and/or it can be used in organic waste sources in operations such as drying manure filtrate. Furthermore, this biogas can be used for heating, power generation, or in subsequent synthetic or catalytic processes. The prevention of gas releases from organic waste sources leads to the additional advantage of satisfying the public demand for acrid odor reduction in, or even its elimination from, organic waste sources.
The minimization or reduction of gas emissions by this invention is further facilitated by the reliance on either no lagoons or on reduced-size lagoons. When this invention relies on reduced-size lagoons, gas emissions from such lagoons are reduced or eliminated because this invention reduces anaerobic lagoon loading and lagoon surface area by comparison to loading and surface area of conventional lagoons. Reliance on reduced-size small load lagoons makes anaerobic lagoons economically feasible and extends the lagoon useful life with respect to that of large conventional lagoons. Furthermore, it leads to an increase in the available surface area of useful space at the organic waste treatment site and to a minimization or elimination of the risk of water contamination by spills or leaks that are more difficult to control in large, big-load conventional lagoons. Because this invention does not rely on conventional biological and volume reduction treatments in anaerobic lagoons, biogas emission from conventional lagoons is eliminated.
It is a further objective of this invention to provide a waste treatment process in which the separation of solids is accomplished with very high settling rates. Accordingly, the liquid-solid separation of the organic waste is improved with respect to that achieved by most conventional organic waste treatment processes. Furthermore, the effluents separated from the organic waste according to this invention can be used in irrigation and wetland projects under current EPA discharge standards and salting problems in recycling streams are eliminated. The separation process of this invention can also be used to remove undesirable components from municipal sludge.
One of the features of this invention is that the treatment of organic waste can be accomplished by using waste materials from other sources, such as mining waste and fly ash. This feature leads to a more advantageous and effective waste treatment because mining waste and fly ash would otherwise generate disposal problems.
It is a further objective of this invention to convert organic waste into an organic-based standard composition, granular, slow release, readily available fertilizer with micro-nutrients whose delivery requires no changes in existing fertilizer delivery systems. More specifically, one of the objectives of this invention is to manufacture and provide a nitrogen-phosphorous-potassium (hereinafter xe2x80x9cNPKxe2x80x9d) fertilizer with sizing materials and, in particular, with zeolite and densifiers. One of the fertilizers produced according to this invention is made from hog waste, zeolite, fly ash, lime, and optionally, off grade commercial fertilizers. In general, the raw ingredients for the fertilizer and food supplement production methods of this invention are economical and the production equipment size is not limited by process engineering.
The fertilizer production methods of this invention are flexible enough as to produce fertilizer products that combine high availability of plant nutrients, slow release characteristics, soil amendment properties, low salinity, and a rich mix of micronutrients in the organic base. Because of the flexibility of the fertilizer production method of this invention, the fertilizer composition can be advantageously tailored to the demands of specific markets.
The waste treatment and fertilizer and food supplement production methods of this invention rely on a variety of mechanical processing equipment that includes processing equipment for efficiently densifying organic waste. This feature leads to the advantageous improvement of the organic waste handling characteristics and facilitates the retention of zeolites, magnesium, phosphates and ammonia in the organic waste throughout the process, thus becoming part of a finished fertilizer.
A feature of the mechanical processing equipment of this invention is that it can operate in either continuous or batch mode. Accordingly, an advantage of the organic waste treatment and fertilizer and feed supplement production methods of this invention is that they can be implemented in small farms as well as in large farms, batch operations being more useful for small farms and continuous operations being more useful for large farms.
It is a further objective of this invention to provide organic waste treatment and fertilizer and food supplement production methods that can absorb the organic waste production from a great diversity of organic waste sources, whether the organic waste sources are small or large scale operations, and regardless of whether the organic waste is produced at the organic waste treatment site or at a plurality of near or remote organic waste sources. A feature of the methods of this invention is that their implementation is versatile enough as to be adaptable to different economic strategies and needs, whether it is in organic waste sources that are being built or in already existing organic waste sources by simple retrofitting. With this versatility, an advantage of the methods of this invention is that they can easily be implemented for reclaiming existing sites that are destined to either closure or cleanup.
When implemented in conjunction with farms or livestock operations, the integrated waste treatment and fertilizer and food supplement production methods of this invention successfully density and dry manure slurry, significantly improve animal health, feeding efficiency and reproductive capacity, and they lead to the production of an economically competitive organic-based slow release fertilizer and optionally, to the production of feed supplements. These features permit to advantageously improve the overall economics of livestock production by improving animal health, decrease waste management costs, implement processes that easily comply with environmental regulations, reduce long term liability by reducing or eliminating water and soil contamination, and use waste material to profitably produce NPK fertilizer and optionally feed supplements.
The objectives of this invention are specially significant to the pork producing sector of the US and most countries. The biggest concerns of pork producers include: Competition for land space between farms and urban development, environmental problems, competitive marketing of products, and proper care of animal diseases and animal health. Because the present invention significantly reduces the size of conventional lagoons, or even eliminates the need for lagoons, its embodiments need much less surface area than that required by conventional methods.
The positive environmental effects of the present invention are manifest in three forms: The minimization, or even elimination, of emission of gases that would otherwise have detrimental environmental effects and would be a nuisance to human beings; the recovery of energy-rich gases whose subsequent utilization reduces reliance on other forms of energy, and the discharge of effluents with reduced nutrient loading. Reduction of nutrient loading in final effluents can largely eliminate nutrient accumulation problems when the effluents are used for irrigation or when the effluents are used to make constructed wetlands economically viable.
The effects of this invention on marketing pork products include the ability to raise animals in less remote areas because of its environmentally friendly waste treatment method, the production of low cost high-quality fertilizer, and the optional production of feed supplement that lead to a reduction of the operational costs. Furthermore, animal diseases are reduced and animal health is improved because of the improved conditions in barn air quality.
The objectives of this invention are achieved by means of an integrated waste treatment method that relies on modern technology and that can be used in operations that range from small scale to large scale operations. In particular, the objectives of this invention are achieved by a specially designed mechanical system which facilitates the implementation of a method for separating organic waste into a liquid and a precipitate. The precipitate includes the products of reacting the organic waste with flocculant, phosphate precipitating agent, ammonia retaining agent, base and optionally a densifier.
Optionally, gas reactors recover methane-rich biogas that can be used in heating, power generation, or subsequent synthetic or catalytic processes.
The liquid, optionally treated in a reduced load lagoon system, can subsequently be used in irrigation, wetland projects, or recycled in the organic waste source. The precipitate yields a solid fertilizer base which can be used as such as a fertilizer or it can be mixed with other compounds such as nitrogen, potassium, or phosphorous containing compounds as well as micronutrients to improve its grade as a fertilizer.
Subsequent steps include pelletizing and drying the mixture and controlling its size to obtain standard size fertilizer pellets. The final product is an organic-based, granular, slow release fertilizer whose composition includes micronutrients. This fertilizer is readily available to plants and it can have a standard composition and grain size. The solid obtained from the filtration of the solid fraction can be adjusted to a proper pH, if needed, and used as a feed supplement.
Whether this invention is implemented for the production of fertilizer, feed supplement, or both, one of the objectives of this invention is nitrogen conservation. To conserve nitrogen, this invention preferably relies on the addition of zeolite, optimally an ammonia adsorbing zeolite, to one or several of the different organic waste generation steps. For example, zeolite can be added to animal feed, it can be incorporated into farm waste streams, and/or used in the waste treatment process itself. Added zeolite retains nitrogen which would otherwise be released mostly in the form of gaseous ammonia. The nitrogen retention achieved by the method of this invention contrasts with traditional waste treatment methods which allow for a significant release of ammonia. In these traditional operations, release of ammonia may account for a significant loss of the nitrogen initially contained in the organic waste, an ammonia loss that can be about 70%. Furthermore, the capture of ammonia can be increased according to the methods of this invention by reacting ammonia with acids such as sulfuric and phosphoric acids.
Additional objects, features and advantages of this invention will become apparent to persons of ordinary skill in the ale upon reading the remainder of the specification and appended claims and upon referring to the attached Figures, or may be learned by the practice of the invention as set forth hereinbelow.